I found this when i went googling
I don't know what part of Qld you live in, but if you live in Brisbane get in touch with the City Council and they'll be able to help you with places that might sell them. Or you could look in the white pages under worm farms. They mightn't have silkworms, but could probably point you in the right direction.
Not Victoria, but certainly the advice was sound.
Hope this helps out ! Also, try any dragon rescues, and the zoos. I'll bet they have a source
Janie.